1. Field of the Invention
The invention relates to a hydrodynamic clutch.
2. Description of the Related Art
Hydrodynamic clutches are known. They comprise an impeller and a turbine wheel which, as a rule, are the two only blade wheels of the hydrodynamic clutch. Accordingly, no stator is provided.
As a rule, the impeller and the turbine wheel jointly form a toroidal working chamber which is or can be filled with a working medium, for example oil, water or water-mixture. In the impeller the working medium is accelerated in radial direction outward, enters into the turbine wheel where it is slowed in radial inward direction and again enters into the impeller. By means of this working medium circulation the torque or respectively power is transferred free from wear and tear, from the impeller to the turbine wheel.
In the known state of the art, stationary or movable throttle plates are provided in hydrodynamic clutches in order to influence the working medium circulation and thereby the transfer behavior of the hydrodynamic clutch, especially to specifically adjust it. DE 103 53 518 A1 for example, describes two alternative options of providing throttle plates. According to a first embodiment stationary throttle plates which are located in axial direction of the hydrodynamic clutch, or in radial direction of the hydrodynamic clutch are provided which, depending on the slippage between impeller and turbine wheel exert a more or less throttling effect upon the working medium circuit. According to the second embodiment movable wall sections of the impeller wheel are provided, in order to influence the working medium circuit.
The disclosure document WO 2005/050047 A1 describes throttle plates extending in radial direction of the hydrodynamic clutch, which can be moved alone or jointly with a part of the impeller or turbine wheel of the hydrodynamic clutch in order to be optionally introduced into the circuit flow of working medium in the working chamber, thereby influencing the transfer behavior of the hydrodynamic clutch.
In the first-mentioned embodiment according to DE 103 53 518 A1 with stationary axially aligned throttle plates a targeted adjustment of the transfer behavior of the clutch is possible only to a limited extent. On the contrary, a firmly predetermined dependency on the effect of the throttle plate on the slippage results. Even the suggested displacement of parts of the blade wheel wall of the impeller, especially in the area of the radial outer diameter of the hydrodynamic clutch, or respectively its working chamber permits only a limited exertion of influence upon the transfer behavior.
In the embodiment according to the aforementioned WO-publication 2005/050047 A1 a comparatively great force is required to displace the throttle plate in axial direction due to the radial orientation of the throttle plate. As a rule, the fill level in the hydrodynamic clutch—that is the volume of working medium which circulates in the working chamber—must therefore be reduced, in order to be able to implement the axial movement of the throttle plate.
The disclosure document DE 103 53 554 A1 according to one embodiment describes a ring-shaped throttle plate which comprises a horizontal segment of an annular slide extending in circumferential direction of the hydrodynamic clutch and which is operable through an adjustment mechanism that is located radially outside the working chamber.
The patent documentation DE 582 886 describes a throttle plate which, in circumferential direction of the hydrodynamic clutch progresses in the area of a central diameter of the working chamber and from the perspective of an axial section across the hydrodynamic clutch extends with its intake side against which the circulation flow of working medium flows, parallel to the axis of rotation of the hydrodynamic clutch. In order to move the throttle plate into its active position, it is displaced out of the working chamber into a core ring area which is limited by a wall in relation to the working chamber. In its inactive position the throttle plate is not immediately surrounded by the flow zones of the working chamber, but is separated from them by the wall which forms the core ring area. The demonstrated embodiment requires a high constructive expenditure.
It is an objective of the current invention to provide a hydrodynamic clutch including a throttle plate to influence the transmission ratio of the hydrodynamic clutch. On the one hand a great effect upon the transmission behavior, that is the power transmitted from the impeller to the turbine wheel, or respectively the transmitted torque is possible through axial displacement of the throttle plate inside, or respectively into the working chamber. On the other hand a slight displacement of the throttle plate in any operating status and at any fill level of the hydrodynamic clutch is ensured. In addition an embodiment of the hydrodynamic clutch is created which is constructively simple and as compact as possible.
The inventive hydrodynamic clutch comprises an impeller and a turbine wheel which jointly form a toroidal working chamber that can be or is filled with a working medium. A throttle plate is provided which can be moved in axial direction of the hydrodynamic clutch in order to be optionally introduced into the working chamber and/or to be displaced within the working chamber.
According to the invention the throttle plate extends in the circumferential direction of the hydrodynamic clutch, that is around the rotational axis of the hydrodynamic clutch, as a rule in a ring shape, elliptical shape or also in a square shape. The throttle plate can be a continuous design or can be discontinuous in circumferential direction of the hydrodynamic clutch.
According to the invention the throttle plate is provided in the area of the central diameter of the working chamber. This means it is located with a distance relative to the outside diameter of the working chamber and relative to the inside diameter of the working chamber.
The throttle plate extends in an axial direction of the hydrodynamic clutch. This means it comprises an intake side against which the working medium flows, thus creating a circulation in the working chamber and which, from the perspective of an axial section across the hydrodynamic clutch extends parallel to the axis, or substantially parallel to the rotational axis of the hydrodynamic clutch. The axial section is carried through the rotational axis of the hydrodynamic clutch. The term “parallel to the axis” is understood to be not only an exact parallelism with the axis, but also a certain angular arrangement of the intake side of the throttle plate relative to the rotational axis of the hydrodynamic clutch is possible. The more defined the angle, the stronger is the force which is required to displace the throttle plate in the axial direction. The angle should therefore be relatively small. In each instance it is to be less than 90°, for example between 0 and 45°, especially between 0 and 30° and especially advantageously between 0 and 10°, or 0 and 5° relative to the rotational axis of the hydrodynamic clutch.
The hydrodynamic clutch can be in the embodiment of a hollow cylinder or a sector of a hollow cylinder, for example a plurality of individual sectors of a hollow cylinder. In both cases the distance of the throttle plate from the rotational axis of the hydrodynamic clutch is constant over the entire circumference of the hydrodynamic clutch. Obviously, other forms with varying distance relative to the rotational axis over the circumference of the hydrodynamic clutch are considered. In angular arrangements, for example, conical forms of sections of cones are considered.
The throttle plate is advantageously supported by an adjustment mechanism and/or is connected to such a mechanism which engages with the throttle plate in a central area in a radial direction from the inside and/or a radial direction from the outside. The throttle plate, jointly with the component of the adjustment mechanism engaging with it forms in particular a T, viewed in an axial perspective through the hydrodynamic clutch, or respectively in circumferential direction through the throttle plate and the adjustment mechanism.
According to the invention the throttle plate—especially in the latter design variation—can be moved from an inactive position which is located in the area of the separation gap between the impeller and the turbine wheel of the hydrodynamic clutch into an active position, which is provided in the impeller or turbine wheel in the area of a central diameter of the working chamber. The required physical axial space for the throttle plate in its active position throttling the circulation of working medium, as well as in its inactive position which does not inhibit the circulation of working medium in the working chamber is hereby minimal, especially since the path of movement of the throttle plate is located entirely or substantially entirely, at least in axial direction or in any direction of the hydrodynamic clutch inside the working chamber.
The throttle plate is located directly in the working chamber in its active position, as well as in its inactive position. This means that it is not separated by a wall or something similar from the working chamber. On the contrary, from the perspective of an axial section across the hydrodynamic clutch the working chamber possesses a cross section that is without a central area which is delimited by a wall. Therefore, the throttle plate in its inactive, as well as in its active position is directly surrounded by the flow zones of the working chamber, in other words, without insertion components between them. Advantageously, the throttle plate is movable only inside the working chamber.
In an especially advantageous embodiment, the cross section of the working chamber, from the perspective of an axial section across the hydrodynamic clutch displays a full circular shape or respectively a full surface form, which could result from an elliptical shape or respectively from a shape deviating from the circular shape. These statements refer to one respective halve of the hydrodynamic clutch since in this axial perspective, the cross section of the working chamber naturally occurs respectively once on each side of the rotational axis of the hydrodynamic clutch.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrates embodiments of the invention (, in one form,) and such exemplifications are not to be construed as limiting the scope of the invention in any manner.